Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, and so forth. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) systems including Evolved Universal Terrestrial Radio Access (E-UTRA) and orthogonal frequency division multiple access (OFDMA) systems.
An orthogonal frequency division multiplex (OFDM) communication system effectively partitions the overall system bandwidth into multiple subcarriers, which may also be referred to as frequency sub-channels, tones, or frequency bins. For an OFDM system, the data to be transmitted (e.g., the information bits) is first encoded with a particular coding scheme to generate coded bits, and the coded bits are further grouped into multi-bit symbols that are then mapped to modulation symbols. Each modulation symbol corresponds to a point in a signal constellation defined by a particular modulation scheme (e.g., M-PSK (Phase Shift Keying) or M-QAM (Quadrature Amplitude Modulation) in which M may be a power of two) used for data transmission. At each time interval that may be dependent on the bandwidth of each frequency subcarrier, a modulation symbol may be transmitted on each of the frequency subcarriers. Thus, OFDM may be used to combat inter-symbol interference (ISI) caused by frequency selective fading, which is characterized by different amounts of attenuation across the system bandwidth.
Generally, a wireless multiple-access communication system can concurrently support communication for multiple wireless terminals that communicate with one or more base stations via transmissions on forward and reverse links. The forward link (or downlink) refers to the communication link from the base stations to the terminals, and the reverse link (or uplink) refers to the communication link from the terminals to the base stations. This communication link may be established via a single-input-single-output, multiple-input-single-output or a multiple-input-multiple-output (MIMO) system.
A MIMO wireless system employs a number (NT) of transmit antennas and a number (NR) of receive antennas for data transmission. A MIMO channel formed by the NT transmit and NR receive antennas may be decomposed into NS spatial streams, where, for all practical purposes, NS<=min {NT, NR}. The NS spatial streams may be used to transmit NS independent data streams to achieve greater overall throughput.
A MIMO system also supports time division duplex (TDD) and frequency division duplex (FDD) systems. In a TDD system, the forward and reverse link transmissions are on the same frequency region so that the reciprocity principle allows estimation of the forward link channel from the reverse link channel. This enables an access point (AP) to extract transmit beam-forming gain on the forward link when multiple antennas are available at the AP. In a FDD system, the forward and reverse link transmissions are on different frequency regions. Therefore, forward link and reverse link channels may be estimated explicitly.
Multimedia Broadcast/Multicast Services (MBMS) provide simultaneous delivery of multimedia content to a large set of receivers. The MBMS can be split into three general areas-bearer services, delivery methods, and user services and applications. An MBMS bearer service provides a bit pipe for the transport of Internet protocol (IP) traffic to a group of receivers in an efficient manner. Two delivery methods may be defined in MBMS, such as streaming and file downloading. The streaming delivery method defines the protocols for the delivery of multimedia content for immediate consumption such as in a Mobile television channel. The file download delivery method enables a file streaming of multimedia files for storage and delayed consumption at the receiver. An MBMS user service is able to employ different delivery methods, unicast connections and MBMS bearer services for providing the desired application to a user.